1. Field of the Invention
The present invention relates to a vapor compression refrigerating apparatus (supercritical refrigerating cycle) in which a pressure inside a radiator (high pressure side) exceeds a critical pressure of a refrigerant. Preferably, the present invention is applicable to an automotive air conditioner.
2. Description of Related Art
One type of known supercritical refrigerating apparatus is disclosed in JP-A-10-115470 (U.S. patent application Ser. No. 08/916634).
Such conventional apparatus has a first pressure control valve, which reduces the pressure of the refrigerant flowed from a radiator, for controlling pressure at a radiator outlet according to a refrigerant temperature at the radiator outlet, and has a receiver for storing the refrigerant flowed from the first pressure control valve by separating liquid refrigerant and gaseous refrigerant. It also has a second pressure control valve, which reduces the pressure of the refrigerant flowed from the receiver, for controlling refrigerant flow rate such that the superheating of the refrigerant at a compressor inlet is kept constant.
According to the conventional apparatus, however, the supercritical refrigerating cycle is controlled by using two pressure control valves for one evaporator. Thus, when the conventional apparatus is simply applied to a supercritical refrigerating cycle having two evaporators, it is necessary to have a pressure control valve for controlling the refrigerant pressure at the radiator outlet, and two pressure control valves for controlling the superheating of the refrigerant at respective evaporator outlets. In other words, the number of the valve increases as the number of the evaporator increases.